Vertically adjustable tables, thus requiring vertically adjustable legs, are known and used typically as computer stands, drafting tables, physical therapy tables, etc. Although a single leg may be adjusted, typically all legs are interconnected and adjusted simultaneously an equal amount thereby moving the tabletop up or down as desired.
Known tables have non-rotatable, hollow, telescopic leg members. A threaded nut is fixed near the inside top of the lower member. A threaded rod is threaded through the nut and extends into the hollow portion of each of the leg members. A sprocket is fastened at the top of the threaded rod and is driven by a common chain which drives similar sprockets on all legs. The upper leg member is fastened to the tabletop, and it prevents the lower leg member from rotating, when the threaded rod is rotated, by cooperation between a keeper and keeper slot in the lower and upper leg members, respectively. The Assignee of this application presently markets a physical therapy table of this type. U.S. Pat. Nos. 2,721,106 and 3,587,482 disclose variations of a similar table.
The problem with the legs on these known tables is that the range of height adjustment is too limited when the lowest level is maintained at an advantageous low level. Particularly with respect to a physical therapy table, greater height adjustment is advantageous when the lowest level is no greater than the height of the seat surface of a wheelchair. To achieve greater height adjustment with the known design, the threaded rod must be longer, but that requires the lowest level of the table to be too high.